The answer to 'how to kill bee' is to call a professional pest control technician. Bees are important pollinators, so it's best to avoid killing them yourself unless absolutely necessary. Attempting to kill bees on your own can be dangerous and may cause them to become aggressive. Professional pest control technicians have the proper training and equipment to safely remove or eliminate a bee problem.
If you do need to address a bee issue on your own, the safest approach is to use an insecticide spray specifically formulated for bees. Apply the spray directly to the nest or hive in the early morning or late evening when bees are less active. Wear protective clothing like long sleeves, pants, and gloves to avoid getting stung. Be very careful and keep a safe distance, as disturbing a bee colony can cause them to become defensive. If you're not comfortable with this process or the bee problem persists, it's best to call in a professional pest control expert.